1. Field of the Invention
The present invention relates to a compostable container for containing liquids or liquid containing materials. The present invention furthers relates to a paperboard container having a degradable coating on at least one of the internal or external surfaces thereof. More particularly, the present invention relates to a paperboard container which will biodegrade to carbon dioxide, water and biomass under composting conditions. The present invention further relates to a method of making and a method of using the degradable container.
2. Discussion of the Prior Art
In the management of Municipal Solid Waste (MSW), the expectation that paper and paper products would biodegrade in landfills has proven to be unreliable. In fact, newspapers buried for over fifty year have been recovered from landfills in readable condition. Since paper comprises about 50 % of landfill space, it has become an important priority to find alternate ways to manage paper waste.
Recycling paper, often with the removal of printing inks and coatings, has proven to be economically feasible when the recovered pulp fibers find new markets and applications. Fiber recovery, and, in particular, repeated fiber recoveries tend to damage, break, and otherwise reduce the quality of paper fiber. This degradation in paper quality often results in a product with limited or nonexistent new markets or applications.
Since paper has the inherent property of biodegradability under appropriate conditions, more attractive alternates to simple landfilling have received increased attention. Among these, is the process of composting, in which waste is degraded to humus or biomass under accelerated and controlled conditions of moisture, air and microorganisms. More specifically, paper, under composting conditions is converted into carbon dioxide, water, and biomass. The biomass is essentially comprised of microorganisms. Thus, the mass of waste is significantly reduced and the humus by-product has commercial value as low grade fertilizer, soil conditioner, and as a mulch for land and agricultural applications.
Paper products are often coated with resins or plastic materials to provide barrier properties when they will be used in the containment of liquids. The most important requirements for these structures when intended for use as folded cartons to contain liquid products include:
a. barrier properties to reduce and prevent absorption and/or transmission of liquid components; PA1 b. heat sealability for carton construction and integrity. PA1 c. printability to provide attractive, non-functional graphics; PA1 d. vapor barriers to contain fragrances, flavors, moisture, etc.; PA1 e. barriers to oxygen and other ambient gases; PA1 f. rigidity, shape retention, and crush resistance.
Typical constructions of important commercial value include milk cartons in which the paperboard coating composition is low density polyethylene; fruit juice containers as described in U.S. Pat. No. Re 33,376; and wet wipe container as described in copending U.S. patent application Ser. Nos. 07/740,141 now abandoned and 07/923,556, now U.S. Pat. No. 5,286,538 all of which are incorporated herein by reference.
Such constructions meet the requirements stated above in (a)-(f), however, such constructions are compostable only to the degree to which cellulose pulp is present, typically around 85% Under composting conditions, the pulp fibers would be expected to decompose leaving a residue of biologically inert plastic.